Are you using hCG on your cruise? No matter the Test dose, you are putting exogenous testosterone in your body and it is going to shut down your natural production. I don't think that the extent of testicular atrophy is dose dependent. Meaning: more test doesn't equal more shrinkage. I could be wrong, but that is my understanding.
My balls shrank at 140mg/wk TRT dose, and haven't gotten any smaller since I bumped it up to 500mg/wk a few weeks ago.
The only way to combat testicular atrophy is to use hCG to at least maintain some natural hormone production.